Exploring minimal nonverbal interruption in HRI

Designing robotic behaviours capable of initiating an interruption will be extremely important as robots increasingly interact with people. Consequently, we explore the social impact of a minimal set of physical nonverbal cues that can be exhibited by a robot to initiate robot-human interruption: (a) speed of motion, (b) gaze, (c) head movement, d) rotation and (e) proximity to the person. We present two related studies evaluating this set. First, for requirements gathering, we observed the behaviour of interruption between humans, with a human actor attempting to interrupt other humans while being constrained to use only a set of behavioural cues that could be mimicked by a simple nonverbal robot. Next, we programmed a robot to exhibit similar social physical nonverbal cues, and tested their feasibility in a user study of robotic nonverbal interruption across interruption scenarios. Our results show that people were able to interpret interruption urgency from robot behaviour using only minimal nonverbal behavioural cues. These findings contribute to informing future designs of social human-robot interfaces.